Process for the production of butene-1 from a mixture of C4 olefins

ABSTRACT

A simplified process for jointly producing butene-1 and ether in a catalytic distillation zone which comprises an upper catalytic zone for etherification and a lower catalytic zone for isomerization of C 4  plus olefins. The process is especially usefull when combined with a process for the production of light olefins including ethylene and propylene from methanol. According to the invention, the produced butene-1 stream is combined with ethylene to produce polyethylene.

FIELD OF THE INVENTION

This invention relates to an improved process for the conversion ofhydrocarbons, and more specifically for the catalytic isomerization ofolefinic hydrocarbons.

BACKGROUND OF THE INVENTION

Olefinic hydrocarbons are feedstocks for a variety of commerciallyimportant additional reactions to yield fuels, polymers, oxygenates andother chemical products. The specific olefin isomer, considering theposition of the double bond or the degree of branching of thehydrocarbon, may be important to the efficiency of the chemical reactionor to the properties of the product. The distribution of isomers in amixture of olefinic hydrocarbons is rarely optimum for a specificapplication. It is often desirable to isomerize olefins to increase theoutput of the desired isomer.

Butenes are among the most useful of the olefinic hydrocarbons havingmore than one isomer. A high-octane gasoline component is produced froma mixture of butenes in many petroleum refineries principally byalkylation with isobutane; 2-butenes (cis- and trans-) generally are themost desirable isomers for this application. Secondary-butyl alcohol andmethylethyl ketone, as well as butadiene, are other importantderivatives of 2-butenes. Demand for 1-butene has been growing rapidlybased on its use as a co-monomer for linear low-density polyethylene andas a monomer in polybutene production. Isobutene finds application insuch products as methyl methacrylate, polyisobutene and butyl rubber.The most important derivative influencing isobutene demand and buteneisomer requirements, however, is methyl t-butyl ether (MTBE) which isexperiencing rapid growth in demand as a gasoline component. Pentenesalso are valuable olefinic feedstocks for fuel and chemical products.

Catalytic isomerization to alter the ratio of isomers is one solution tothis need. Since ethers must be supplied at lower cost to findwidespread use as a fuel product and since isomerization competes withincreased feedstock processing as a source of desired isomers, anisomerization process must be efficient and relatively inexpensive. Inone aspect, a catalytic isomerization process must recognize olefinreactivity: isobutene in particular readily forms oligomers which couldrequire a reconversion step to yield monomer if produced in excess. Theprincipal problem facing workers in the art, therefore, is to isomerizeolefins to increase the concentration of the desired isomer whileminimizing product losses to heavier or lighter products.

U.S. Pat. No. 4,797,133 discloses a process for the recovery of butene-1from a mixed C₄ feed stream which also contains isobutylene, butene-2,isobutane, and normal butane. The C₄ feedstream is passed through anetherification zone to selectively convert isobutylene to an ether toproduce a first stream comprising the product ether and C₄ hydrocarbonsand a second stream comprising isobutane and butene-1. The second streamis then separated to yield butene-1. The first stream is alkylated foruse in a motor fuel. Butene-2 isomers (cis- and trans-) are desiredfeedstocks to an alkylation reactor in which the butene-2 isomers reactwith isobutane to produce alkylate.

U.S. Pat. No. 4,423,264 discloses a process for the production of a purebutene-1 and a premium gasoline from a C₄ olefinic hydrocarbon fraction.According to the disclosure, the C₄ olefinic hydrocarbon fraction ispolymerized and disproportionated to partially convert the isobutene toa gasoline/jet fuel boiling range component (e.g., an isobutene dimerand trimer), hydrogenating the gasoline/jet fuel boiling range fractionto produce a stabilized fuel component, and fractionating the remainingC₄ olefins to obtain a high purity butene-1 product.

U.S. Pat. No. 5,523,502 discloses a process for the deep catalyticcracking of petroleum feedstocks to produce a full range of synthetichydrocarbons including a C₄ hydrocarbon fraction which includes C₄paraffins and butenes. In processing the C₄ hydrocarbon fraction,combinations of separate processing includes: hydroisomerization ofbutene-1 to butene-2, butadiene hydrogenation, and etherification. Theremaining butenes are passed to an extractive distillation process toseparate the olefins (butene-1 and butene-2) from any paraffins (normalbutane, etc.), and the olefins are passed to a skeletal isomerizationunit and therein converted to isobutene which is recycled to theetherification zone to produce more MTBE.

Processes for the isomerization of olefinic hydrocarbons are widelyknown in the art. Many of these use catalysts comprising phosphate. U.S.Pat. No. 2,537,283 (Schaad), for example, teaches an isomerizationprocess using an ammonium phosphate catalyst and discloses examples ofbutene and pentene isomerization. U.S. Pat. No. 3,211,801 (Holm et al.)discloses a method of preparing a catalyst comprising precipitatedaluminum phosphate within a silica gel network and the use of thiscatalyst in the isomerization of butene-1 to butene-2. U.S. Pat. Nos.3,270,085 and 3,327,014 (Noddings et al.) teach an olefin isomerizationprocess using a chromium-nickel phosphate catalyst, effective forisomerizing 1-butene and higher alpha-olefins. U.S. Pat. No. 3,304,343(Mitsutani) reveals a process for double-bond transfer based on acatalyst of solid phosphoric acid on silica, and demonstrates effectiveresults in isomerizing 1-butene to 2-butenes. U.S. Pat. No. 3,448,164(Holm et al.) teaches skeletal isomerization of olefins to yieldbranched isomers using a catalyst containing aluminum phosphate andtitanium compounds. U.S. Pat. No. 4,593,146 teaches isomerization of analiphatic olefin, preferably 1-butene, with a catalyst consistingessentially of chromium and amorphous aluminum phosphate. None of theabove references disclose the olefin-isomerization process using thenon-zeolitic molecular sieve (NZMS).

The art also contains references to the related use of zeoliticmolecular sieves. U.S. Pat. No. 3,723,564 (Tidwell et al.) teaches theisomerization of 1-butene to 2-butene using a zeolitic molecular sieve.U.S. Pat. No. 3,751,502 (Hayes et al.) discloses the isomerization ofmono-olefins based on a catalyst comprising crystalline aluminosilicatein an alumina carrier with platinum-group and Group IV-A metalliccomponents. U.S. Pat. No. 3,800,003 (Sobel) discloses the employment ofa zeolite catalyst for butene isomerization. U.S. Pat. No. 3,972,832(Butler et al.) teaches the use of a phosphorus-containing zeolite forbutene conversion in which the phosphorus has not been substituted forsilicon or aluminum in the zeolite framework. U.S. Pat. No. 5,292,984discloses the use of a non-zeolitic molecular sieve, NZMS, for theisomerization of pentenes in a pentene-containing feedstock comprising araffinate from an etherification process. U.S. Pat. No. 5,292,984, whichis hereby incorporated by reference, discloses the use of a catalystcomprising at least one NZMS and having the absence of a platinum-groupmetal demonstrates surprising efficiency in converting butene-2 toisobutene or butene-1 in a butene isomerization operation and in theskeletal isomerization of pentenes.

Efficient production of butene-1 has remained a problem in the art,requiring complex, multi-step processes to recover butene-1, often as aby-product of motor fuel production. In such processes, the objective isbutene-2 which can be alkylated to produce a high octane, low vaporpressure product. Often when butene-1 is isolated, it is furtherskeletally isomerized to produce more isobutene.

It is the objective of the present invention to provide a simplifiedprocess for the recovery of butene-1 from C₄ olefin streams. It is afurther objective of the present invention to provide a reduced costprocess for selectively and directly producing butene-1 from C₄ olefinichydrocarbon streams.

SUMMARY OF THE INVENTION

This invention provides a novel, simplified process for the productionof butene-1 from a C₄ olefin stream consisting of isobutene, butene-1,butene-2, butadiene, and pentenes. Such streams are generally derivedfrom methanol-to-olefin processes which convert methanol, dimethyl etherand the like to light olefins. The light olefin streams produced in thismanner have very small amounts of paraffin components in any singlecarbon number group and consist essentially of ethylene, propylene,butenes and pentenes, with less than 1-5 mol-% paraffins produced in anysingle carbon range. The invention is based on the integration ofetherification and butene isomerization into a single catalyticdistillation zone wherein the isobutene is reacted with an alcohol suchas methanol to produce a tertiary alkyl ether and the remaining butenesare selectively isomerized in the presence of hydrogen to butene-1. Thehydrogen is introduced to the catalytic distillation zone by injectinghydrogen into a liquid side draw stream and returning the hydrogenadmixture directly to the isomerization zone to avoid hydrogendistribution problems. Butene-1 and unreacted methanol are withdrawnfrom the upper section of the catalytic distillation zone. The inventionis based on the recognition of the synergy in making the combination ina single catalytic distillation zone. In one embodiment, the singlecatalytic distillation zone comprises an external isomerization reactionzone in fluid communication with the single catalytic distillationcolumn. The ether is withdrawn from the bottom of the catalyticdistillation zone along with any dimer formed by the contact ofbutadiene with the isomerization catalyst. In an alternate embodiment, aselective hydrogenation catalyst can be combined with the isomerizationcatalyst to increase the yield of butene-1. Following the removal of theoxygenate from the butene-1, the butene-1 can be withdrawn as a finishedproduct or polymerized with ethylene to produce polyethylene.

In one embodiment, the invention is a process for the production ofbutene-1 from a feedstream comprising butene-1, butene-2, isobutylene,and pentenes. The process comprises a series of steps. The feedstreamand an alcohol stream at effective separation and etherificationconditions is passed to a catalytic distillation zone having an uppercatalytic zone and a lower catalytic zone. In the catalytic distillationzone at least a portion of the feedstream is contacted in the uppercatalytic zone which contains an etherification catalyst. In the uppercatalytic zone the isobutylene is etherified with the alcohol stream toproduce a tertiary alkyl ether. The remaining portion of the feedstreamin the presence of hydrogen and at effective isomerization conditions iscontacted in the lower catalytic zone. The lower catalytic zone containsan isomerization catalyst for the isomerization of butene-2 to butene-1to produce an additional amount of butene-1. A bottoms product streamcomprising pentenes and tertiary alkyl ether is recovered from thecatalytic distillation zone. A top stream is recovered from thecatalytic distillation zone comprising hydrogen. A side draw streamcomprising alcohol and butene-1 is withdrawn at a point above the uppercatalytic zone. The side draw stream is passed to an alcohol recoveryzone to provide a butene-1 product stream and an oxygenate stream; andat least a portion of the oxygenate stream is returned to the catalyticdistillation zone to provide at least a portion of the alcohol stream.

In another embodiment, the invention is a process for the production oflight olefins comprising ethylene, propylene, and butylene from theconversion of oxygenates. The process comprises a series of steps. Atleast a portion of an oxygenate feedstream comprising methanol orethanol in the presence of a diluent at effective conditions is passedto an oxygenate conversion zone containing a SAPO catalyst to produce areactor effluent stream comprising said light olefins. The reactoreffluent stream is passed to a separation zone to produce an ethylenestream, a propylene stream, and a butylene stream. A portion of theoxygenate feedstream is admixed with at least a portion of the butylenestream comprising isobutylene, butene-1, and butene-2 to provide a feedadmixture. The feed admixture at effective etherification conditions ispassed to a catalytic distillation column having an upper catalyticzone. At least a portion of the feed admixture is contacted in the uppercatalytic zone containing an etherification catalyst and therein theisobutylene is etherified with the oxygenate to produce a tertiary alkylether. The remaining portion of the feed admixture in the presence ofhydrogen and at effective isomerization conditions is contacted in alower catalytic zone containing an isomerization catalyst for theisomerization of butene-2 to butene-1 to produce an additional amount ofbutene-1. A bottoms product stream comprising the tertiary alkyl etheris recovered from the catalytic distillation column. A top stream isrecovered from the catalytic distillation column comprising hydrogen,and a side draw stream is withdrawn at a point above the upper catalyticzone. The side draw stream comprises methanol and butene-1 and is passedto a methanol recovery zone to provide a butene-1 product stream and anoxygenate stream. At least a portion of the oxygenate stream is returnedto the oxygenate conversion zone.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic block flow diagram of the process of the presentinvention.

FIG. 2 is a schematic block flow diagram of the process of the presentinvention with an external isomerization reactor.

DETAILED DESCRIPTION OF THE INVENTION

In the group of olefinic hydrocarbons suitable as feedstock to thecatalytic isomerization process of the present invention, mono-olefinshaving from 4 to 10 carbon atoms per molecule are preferred. Themono-olefins should be present in the feedstock in a concentration offrom about 0.5 to 100 wt-%, and preferably from about 5 to 100 wt-%,with most of the balance usually comprising paraffins. Butenes are anespecially preferred feedstock. The feedstock should be rich in one ormore of the linear butenes, i.e., 1-butene, cis-2-butene andtrans-2-butene, if isobutene is the desired product.

The feedstock olefins may be contained in product streams frompetroleum-refining, synthetic-fuel, or petrochemical operations such ascatalytic cracking, thermal cracking, stream pyrolysis, oligomerization,and Fischer-Tropsch synthesis. Often the feedstock contains paraffinssuch as butanes, pentanes, and C₆ and higher paraffins. An advantageousfeedstock for isobutene or isopentene production is raffinate from anetherification process. The derivation of the feedstock from anetherification process is well known and is described, inter alia, in apaper by Bruno Notari, et al., "Skeletal Isomerization of Olefins," atthe 1980 NPRA Annual Meeting in New Orleans on Mar. 23-25, 1980. Thesestreams may require removal of polar contaminants such as sulfur,nitrogen or oxygen compounds by, e.g., extraction or adsorption tomaintain isomerization-catalyst stability. Raffinate from anetherification process would beneficially be water-washed to removemethanol and other oxygenates present at levels which could affect theperformance of the present catalyst. Removal of dienes and acetylenes,e.g., by selective hydrogenation or polymerization, also may bedesirable.

A detailed description of processes for the production of MTBE fromiso-butylene and methanol, including catalyst, processing conditions,and product recovery, are provided in U.S. Pat. Nos. 2,720,547 and4,219,678 and in an article at page 35 of the Jun. 25, 1979 edition ofChemical and Engineering News. The preferred process is described in apaper presented at The American Institute of Chemical Engineers, 85thNational Meeting on Jun. 4-8, 1978, by F. Obenaus et al. The abovereferences are herein incorporated by reference. Other etherificationprocesses of interest are the production of tertiary amyl methyl ether(TAME) by reacting C₅ iso-olefins with methanol; the production of ethyltertiary butyl ether (ETBE) by reacting C₄ iso-olefins with ethanol; theproduction of tertiary amyl ethyl ether (TAEE) by reacting C₅iso-olefins with ethanol; and, the production of tertiary hexyl methylether (THME) by reacting C₆ iso-olefins with methanol. Etherificationreactions are carried out in the presence of an acid catalyst such as asulfonated, macroporous organic ion exchange resin in the liquid phaseat temperatures between about 30 and about 100° C.

Generally, the production of ethylene is accompanied by the productionof di-olefins such as butadiene. These di-olefins are typically removedprior to the production of any ethers or prior to introducing the buteneand heavier stream to the butene cracking reactor. Butadiene produced inethylene plants by the steam cracking process is present in amountswhich often justify the recovery of the butadiene by extractivedistillation or solvent extraction. U.S. Pat. Nos. 4,038,156 and4,128,457, hereby incorporated by reference, disclose the use of a polarsolvent such as acetonitrile to recover butadiene by extractivedistillation. When C₄ plus olefins are produced in fluid catalyticcracking and methanol to olefins processes, the concentration ofbutadiene is significantly smaller than when they are produced by steamcracking. Butadiene found in such streams is generally removed byselective hydrogenation in the presence of a solid catalyst comprisingnickel and a noble metal such as platinum or palladium or silver asdisclosed in U.S. Pat. No. 4,409,410, hereby incorporated by reference.

Processes for the isomerization are carried out at effectiveisomerization conditions including reaction temperatures generally inthe range of about 50° to 750° C. Selective butene isomerization toproduce 1-butene is effected preferably at temperatures of from 50° to300° C. Pentene isomerization is advantageously performed attemperatures in the range of about 200° to 500° C. Isomerization reactoroperating pressures usually will range from about atmospheric to 50atmospheres. The amount of catalyst in the reactors will provide anoverall weight hourly space velocity of from about 0.5 to 100 hr⁻¹, andpreferably the overall weight hourly space velocity will comprise fromabout 1 to 40 hr⁻¹.

The catalytic distillation column of the present invention is carriedout at effective separation conditions which include a separationtemperature ranging from about 30° C. to about 500° C. and a pressure ofbetween atmospheric to about 50 atmospheres. More preferably, theeffective separation conditions of the present invention include aseparation temperature ranging from about 30° C. to about 300° C. and aseparation pressure ranging from about atmospheric to about 40atmospheres.

According to the present invention, the butadiene can be employed toproduce additional amounts of butene-1 by incorporating the selectivehydrogenation catalyst as described hereinabove in the lower catalystzone of the catalytic distillation zone. In the lower catalytic zone thebutadiene is contacted with the selective hydrogenation zone to produceadditional butenes such as butene-1 and butene-2. As describedhereinabove, the additional butenes are further converted to butene-1 inthe bottom catalytic zone. The selective hydrogenation catalyst may bedisposed as a separate catalyst bed within the lower catalyst zone ormay be admixed with the isomerization catalyst in the lower catalyticzone. Preferably, the ratio of the weight of selective hydrogenationcatalyst to the weight of isomerization catalyst will range from about 1to about 100 and from about 100 to about 1.

In an alternate embodiment, the butadiene in the feedstream can beemployed to produce additional motor fuel components as a dimercomponent. When butadiene is present in the feedstream to the catalyticdistillation, the butadiene is passed to the lower catalytic zone andtherein is converted to a dimer component which is recovered with thebottom product stream from the catalytic distillation zone. The dimercomponent has enhanced motor fuel properties such as reduced vaporpressure and improved octane number over the butadiene and may beblended into motor fuel with the tertiary alkyl ether.

DETAILED DESCRIPTION OF THE DRAWINGS

The process of the present invention is hereinafter described withreference to the figures which illustrate various aspects of the presentinvention. It is to be understood that no limitation to the scope of theclaims which follow is intended by the following description. Thoseskilled in the art will recognize that these process flow diagrams havebeen simplified by the elimination of many necessary pieces of processequipment including valves, some heat exchangers, process controlsystems, pumps, fractionation column overhead and reboiler systems, etc.It may also be readily discerned that the process flow presented in thedrawings may be modified in many aspects without departing from thebasic overall concept of the invention.

Referring to FIG. 1, a feedstream in line 10 is passed to an oxygenateconversion zone 101 via lines 10 and 10'. In the oxygenate conversionzone 101, the oxygenate feedstream in the presence of a diluent isconverted to light olefins. A reactor effluent stream comprisingethylene, propylene, butylene, and pentenes is withdrawn from theoxygenate conversion zone 101 and passed in line 14 to a separation zone102. In separation zone 102 the light olefins are separated in theconventional manner to produce an ethylene stream in line 16, apropylene stream in line 18, and a butylene stream comprising butyleneand pentenes in line 20. The propylene stream is withdrawn as apropylene product stream.

At least a portion of the butylene stream in lines 20 and 20' comprisingisobutenes, butene-1, and butene-2 is admixed with a portion of thefeedstream 10 via lines 10, 50, 12, and 26 to produce a feed admixturein line 24. The feed admixture 24 at effective etherification conditionsis passed to a first reaction zone 103, or pre-etherification reactor,containing an etherification catalyst to at least partially convert aportion of the feed admixture into a tertiary alkyl ether and to producea pre-reactor effluent stream in line 38. The pre-reactor effluentstream is passed to a catalytic distillation zone 106. The catalyticdistillation zone 106 contains an upper catalytic zone 106a located at apoint in the catalytic distillation zone at or about the entry point ofthe feed and a lower catalytic zone 106b located at a point in thecatalytic distillation zone 106 below the entry point of the feed to thecatalytic distillation zone 106. The isobutenes at effectiveetherification conditions react in the upper catalytic zone 106a toproduce additional amounts of tertiary alkyl ether and the butene-2reacts in the lower catalytic zone 106b to produce butene-1 in thepresence of hydrogen which is supplied via line 40. One means ofproviding hydrogen to the lower catalytic zone 106b is shown in FIG. 1.A liquid draw tray, or trap tray, 43 located below the lower catalyticzone 106b collects a liquid side draw stream comprising butene-2.Preferably, liquid draw tray is located at a point in the catalyticdistillation zone 106 where the concentration of butene-2 will be near amaximum concentration. Preferably, the liquid draw tray 43 will belocated between 5 and 15 theoretical trays above the bottom of thecatalytic distillation zone 106, and more preferably, the liquid drawtray is located at a point 8 to 12 theoretical trays above the bottom ofthe catalytic distillation zone 106. A butene-2 stream in line 41comprising butene-2 is withdrawn from the catalytic distillation zone106 at the liquid side draw tray 43. The butene-2 stream is admixed withhydrogen in line 40 to provide a hydrogen admixture and the hydrogenadmixture is passed to pump 108 to provide a lower catalytic zone feedstream in line 40' comprising butene-2 and hydrogen. It is believed thatat least a portion of the hydrogen will be in solution in the lowercatalytic zone feed stream in line 40'. Because the butene-2 stream waswithdrawn at a point below the lower catalytic zone 106b it will have ahigher boiling point than the liquids in the catalytic distillation zonewithin or near the top of the lower catalytic zone 106b. When thebutene-2 stream is returned to the catalytic distillation zone 106 at apoint within or above the lower catalytic distillation, it is believedthat at least a portion of the butene-2, in the presence of hydrogenwill be contacted at effective isomerization conditions with theisomerization catalyst in the lower catalytic zone 106b. Thus, it ispreferred that lower catalytic feed stream 40' is introduced into thelower catalytic zone at a point below the top of the lower catalyticzone 106b, and more preferably, the lower catalytic feed stream isintroduced at a point within the lower catalytic zone 106b. A bottomproduct stream in line 42 comprising the tertiary alkyl ether andpentenes is withdrawn from the catalytic distillation zone 106. Thebottom product stream in line 42 comprising ethers produced in the uppercatalytic zone 106a and C₄ plus olefins such as pentenes may be employedin gasoline blending as a high octane component of motor fuel. A topproduct stream is withdrawn from the catalytic distillation zone 106 inline 46. The top product stream comprises hydrogen and lighthydrocarbons such as methane through isobutane. The top product streamis returned to the separation zone 102 for removal from the process as afuel stream (not shown). A second side draw stream is withdrawn from apoint in the catalytic distillation zone 106 above the upper catalyticzone 106a in line 28. The second side draw stream comprises unreactedoxygenate and butene-1 and is passed to an oxygenate removal zone 105wherein the oxygenates such as methanol, ethanol, or propanol areseparated in the conventional manner from the butene-1 to provide abutene-1 stream in line 32 and an oxygenate stream in line 30. Theoxygenate stream in line 30 is recycled to the catalytic distillationzone 106 by passing the oxygenate stream in lines 30 and 26 to beadmixed with the butenes stream in line 20' to form the feed admixturein line 24. The feed admixture in line 24 is passed to thepre-etherification reactor 103 and the pre-reactor effluent is passed tothe catalytic distillation column 106.

A portion of the ethylene stream in line 16 is passed via line 36 to apolymerization zone 107 containing a polymerization catalyst whereinbutene-1 in line 32 and ethylene in line 36 is polymerized at effectiveconditions to form a polyethylene product stream in line 34. Thepolyethylene product comprises a linear low density polyethylene.

In another embodiment, the catalytic distillation zone includes thecatalytic distillation column and an external isomerization zone, orlower catalytic zone. A portion of butene isomerization may take placeoutside of the catalytic distillation column in the lower catalytic zonewhich is in fluid communication with the catalytic distillation zone.With this option, the hydrogen addition and, optionally, the subsequentstripping of the isomerization reactor effluent is conducted outside ofthe catalytic distillation column and the isomerization reactor effluentis returned to the catalytic distillation column. Referring to FIG. 2, afeedstream in line 110 is passed to an oxygenate conversion zone 201 vialines 110 and 110'. In the oxygenate conversion zone 201, the oxygenatefeedstream in the presence of a diluent at effective oxygenateconversion conditions is converted to light olefins. A reactor effluentstream comprising ethylene, propylene, butylene, and pentenes iswithdrawn from the oxygenate conversion zone 201 and passed in line 114to a separation zone 202. In separation zone 202 the light olefins areseparated in a conventional manner to produce an ethylene stream in line116, a propylene stream in line 118, and a butylene stream comprisingbutylene and pentenes in line 120. The propylene stream is withdrawn asa propylene product stream in line 118.

At least a portion of the butylene stream in lines 120 and 120'comprising isobutenes, butene-1, and butene-2 is admixed with a portionof the feedstream 110 via lines 110, 150, 112, and 126 to produce a feedadmixture in line 124. The feed admixture 124 at effectiveetherification conditions is passed to a first reaction zone 203 orpre-etherification reactor containing an etherification catalyst to atleast partially convert a portion of the feed admixture into a tertiaryalkyl ether and to produce a pre-reactor effluent stream in line 138.The pre-reactor effluent stream is passed to a catalytic distillationcolumn 206. The catalytic distillation zone 206 contains an uppercatalytic zone 206a located at a point in the catalytic distillationzone above the entry point of the feedstream and a lower catalytic zone204, a portion of which is located outside of the catalytic distillationcolumn 206. In the catalytic distillation column 206, the iso-butenereacts at effective conditions with oxygenate in the upper catalyticzone 206a to produce additional amounts of tertiary alkyl ether. A topproduct stream is withdrawn from the catalytic distillation zone 206 inline 146. The top product stream comprises hydrogen and lighthydrocarbons such as methane. The top product stream is returned to theseparation zone 202 for removal from the process as a fuel stream (notshown). A first side draw stream is withdrawn from a point in thecatalytic distillation column 206 above the upper catalytic zone 206a inline 128. The first side draw stream comprises unreacted oxygenate andbutene-1 and is passed to an oxygenate removal zone 205 wherein theoxygenates are separated from the butene-1 in the conventional manner toprovide a butene-1 stream in line 132 and an oxygenate stream in line130. The oxygenate stream in line 130 is recycled to the catalyticdistillation zone by passing the oxygenate stream in lines 130 and 126to be admixed with the butenes stream in line 120. A second side drawstream is withdrawn from the catalytic distillation zone 206 at a pointbelow the feed point (where line 138 enters the catalytic distillationcolumn) and passed at effective isomerization conditions in line 148 andline 150 to an isomerization zone 204, or lower catalytic zone. Hydrogenis injected into the second side draw stream via line 140 to provide thepresence of hydrogen in the isomerization zone 204. The isomerizationzone 204 contains an isomerization catalyst which is selective for theisomerization of butene-2 to butene-1. An isomerization effluent streamin line 142 is withdrawn from the isomerization zone 204 and passed toan optional stripping zone 208 for the removal of light ends andhydrogen as a light ends stream in line 144 and to provide a butenerecycle stream in line 146 which is returned to the catalyticdistillation column 206 at a point between the feed entry point and thepoint from which the second side draw stream in line 148 was withdrawn.Although not repeated in FIG. 2, as shown in FIG. 1, a lower catalyticzone 204 may be present in the catalytic distillation column 206 toimprove the overall isomerization reaction. A bottom product stream inline 142 comprising the tertiary allyl ether and pentenes is withdrawnfrom the catalytic distillation column 206. This bottom product streammay be employed in gasoline blending as a high octane component of motorfuel.

A portion of the ethylene stream in line 116 is passed via line 136 to apolymerization zone 207 containing a polymerization catalyst whereinbutene-1 in line 132 and ethylene in line 136 polymerized at effectiveconditions to form a polyethylene product stream in line 134. Thepolyethylene product stream comprises a linear low density polyethylene.

EXAMPLE

The following example is only used to illustrate the present inventionand is not meant to be limiting. The example was developed usingengineering design calculations based on pilot plant yields for amethanol-to-olefins operation on methanol.

A C₄ ⁺ feedstream separated from the product of a methanol-to-olefinsplant for the conversion of methanol at effective conditions over aSAPO-34 catalyst has the composition shown in the following table in the"FEED" column in terms of units per hour. About 515 units of methanolare combined with the feedstream and the feed admixture is passed to acatalytic distillation zone of the present invention. The catalyticdistillation zone has an upper catalytic zone containing anetherification catalyst to produce about 1500 units/hour of ethers and alower catalytic zone containing an isomerization catalyst and aselective hydrogenation catalyst. Approximately 11 units/hour ofhydrogen are introduced to the lower catalytic zone by injecting thehydrogen into a liquid side draw stream which is withdrawn from thecatalytic distillation zone at a point below the lower catalytic zoneand reintroduced to the catalytic distillation zone at a pointapproximately in the middle or above of the lower catalytic zone.Preferably, the liquid side draw stream is withdrawn at a point wherethe concentration of butene-2 approaches a maximum which will be at apoint between about 8 to about 10 theoretical stages above the bottom ofthe catalytic distillation zone. The process produced about 4560units/hour of a bottoms product stream comprising ethers and C₅ pluscomponents and about 6100 units/hour of butene-1 product. A butene-1water wash step to remove about 5 units/hour of methanol is not shown.In this way, the 270 units/hour of butadiene are converted to mixedbutenes by the selective hydrogenation catalyst and the mixed butenesare isomerized to produce additional butene-1. Without the selectivehydrogenation catalyst in the lower catalytic zone, the butadienes willdimerize to a dimer component and the additional butene-1 will be lostas C₅ plus motor fuel.

    ______________________________________                                        OVERALL MATERIAL BALANCE FOR THE                                                PRODUCTION OF BUTENE-1                                                        (All Flows in units/hour)                                                                              Meth-      Light                                     COMPONENT FEED H.sub.2 anol C5+ Ends Butene-1                               ______________________________________                                        Methanol                 515                                                    Hydrogen  11   1                                                              Isobutane 50    50                                                            Isobutene 400     20                                                          Butene-1 1700     6080                                                        Butene-2 4430   320                                                           Normal-butane 30   30                                                         Butadiene 270                                                                 C.sub.5 Saturates 15   15                                                     Normal pentenes 1090   1090                                                   Iso-pentenes 1330   1330                                                      Cyclopentene 275   275                                                        C.sub.6 plus 610   610                                                        Ethers     1500                                                               TOTAL 10,200  515 4570 51 6100                                              ______________________________________                                    

I claim:
 1. A process for the production of butene-1 from a feedstreamcomprising butene-1, butene-2, isobutylene, and pentenes, comprising thefollowing steps:a) passing the feedstream and an alcohol stream ateffective etherification and separation conditions to a catalyticdistillation zone having an upper catalytic zone and a lower catalyticzone and contacting at least a portion of the feedstream in the uppercatalytic zone containing an etherification catalyst and thereinetherifying the isobutylene with the alcohol stream to produce atertiary alkyl ether; b) contacting the remaining portion of thefeedstream in the presence of hydrogen at effective isomerizationconditions in the lower catalytic zone containing an isomerizationcatalyst for the isomerization of butene-2 to butene-1 to produce anadditional amount of butene-1; c) recovering a bottoms product streamfrom the catalytic distillation zone comprising pentenes and tertiaryalkyl ether; d) recovering a top stream from the catalytic distillationzone comprising hydrogen; e) withdrawing a side draw stream at a pointabove the upper catalytic zone, said side draw stream comprising thealcohol and butene-1; and, f) passing the side draw stream to an alcoholrecovery zone to provide a butene-1 product stream and an oxygenatestream and returning at least a portion of the oxygenate stream tostep(a) to provide at least a portion of the alcohol stream.
 2. Theprocess of claim 1 further comprising polymerizing the butene-1 productstream with an ethylene stream to produce a polyethylene product.
 3. Theprocess of claim 2 wherein the polyethylene product comprises linear lowdensity polyethylene.
 4. The process of claim 1 further comprisingblending the bottoms product stream with at least one gasoline blendingstream selected from the group consisting of a catalytic reformate, acatalytically cracked gasoline, butane, C₅ /C₆ isomerate, and mixturesthereof to produce a motor fuel.
 5. The process of claim 1 wherein thealcohol stream comprises methanol and the tertiary alkyl ether comprisesMTBE.
 6. The process of claim 1 wherein the feedstream comprises lessthan 10 vol-% isobutylene.
 7. The process of claim 1 wherein thefeedstream comprises a C₄ plus stream withdrawn from an oxygenateconversion process for the production of olefins over a SAPO catalyst.8. The process of claim 7 wherein the SAPO catalyst is selected from thegroup consisting of SAPO-34, SAPO-17, and mixtures thereof.
 9. Theprocess of claim 1 wherein the alcohol stream comprises methanol orethanol.
 10. The process of claim 1 further comprising passing thefeedstream and the alcohol stream at effective conditions to apre-etherification reactor containing an etherification catalyst toconvert at least a portion of the feedstream and the alcohol prior topassing the feedstream and the alcohol to the catalytic distillationzone.
 11. The process of claim 1 further comprising withdrawing a secondside draw stream at a point below the lower catalytic zone and passingthe second side draw stream at effective conditions in the presence ofhydrogen to a butene isomerization zone to produce an isomerized streamand returning the isomerized stream to the catalytic distillation zone.12. The process of claim 1 wherein the feedstream further comprisesbutadiene.
 13. The process of claim 12 further comprising contacting thebutadiene in the lower catalytic zone to produce a dimer component andrecovering the dimer component in the bottoms product stream.
 14. Theprocess of claim 12 where the lower catalytic zone further comprises aselective hydrogenation catalyst to convert the butadiene to additionalbutenes and converting the additional butenes to butene-1 in the lowercatalytic zone.
 15. A process for the production of light olefinscomprising ethylene, propylene, and butylene from the conversion ofoxygenates, said process comprising the following steps:a) passing atleast a portion of an oxygenate feedstream comprising methanol orethanol in the presence of a diluent at effective conditions to anoxygenate conversion zone containing a SAPO catalyst to produce areactor effluent stream comprising said light olefins and passing thereactor effluent stream to a separation zone to produce an ethylenestream, a propylene stream, and a butylene steam; b) admixing a portionof the oxygenate feedstream with at least a portion of the butylenestream comprising isobutylene, butene-1, and butene-2 to provide a feedadmixture and passing the feed admixture at effective conditions to acatalytic distillation column having a top and bottom, said catalyticdistillation column having an upper catalytic zone and a lower catalyticzone and contacting at least a portion of the feed admixture in theupper catalytic zone containing an etherification catalyst and thereinetherifying the isobutylene with the oxygenate to produce a tertiaryalkyl ether; c) contacting the remaining portion of the feed admixturein the presence of hydrogen at effective conditions in the lowercatalytic zone containing an isomerization catalyst for theisomerization of butene-2 to butene-1 to produce an additional amount ofbutene-1; d) recovering a bottoms product stream from the catalyticdistillation column comprising the tertiary alkyl ether; e) recovering atop stream from the catalytic distillation column comprising hydrogen;f) withdrawing a side draw stream at a point above the upper catalyticzone, said side draw stream comprising the oxygenate and butene-1; g)passing the side draw stream to an oxygenate recovery zone to provide abutene-1 product stream and an oxygenate stream and returning at least aportion of the oxygenate stream to the oxygenate conversion zone. 16.The process of claim 15 further comprising withdrawing a liquid sidedraw stream comprising butene-2 from the catalytic distillation columnat a point below the lower catalytic zone, admixing the liquid side drawstream with hydrogen to provide a hydrogen admixture, and returning thehydrogen admixture to the catalytic distillation column at a pointwithin the lower catalytic zone.
 17. The process of claim 16 wherein theliquid side draw stream is withdrawn at a point comprising about 5 toabout 15 theoretical trays above the bottom of the catalyticdistillation column.
 18. The process of claim 15 further comprisingpassing the feed admixture to a first reaction zone containing anetherification catalyst to at least partially convert a portion of thefeed admixture prior to passing the feed admixture to the catalyticdistillation column.
 19. The process of claim 15 further comprisingwithdrawing a second side draw stream comprising butene-2 from thecatalytic distillation column at a point about 8 to about 12 theoreticalstages above the bottom and passing the second side draw stream to anexternal isomerization zone in the presence of hydrogen to produce anisomerization effluent stream comprising butene-1 and returning theisomerization effluent stream to the catalytic distillation column. 20.The process of claim 19 further comprising passing the isomerizationeffluent stream to a stripping zone to produce a butene recycle streamdepleted in hydrogen and returning the butene recycle stream to thecatalytic distillation column.
 21. The process of claim 15 furthercomprising polymerizing a portion of the butene-1 product stream with aportion of the ethylene stream to produce a polyethylene product.